Differences Between Late 2015 iMac Retina 4K/5K Models: EveryMac.com
Used Apple A Grade Desktop Computer iMac 27-inch (Retina 5K) 3.2GHZ Quad Core i5 (Late 2015) MK462LL/A 8 GB 1 TB HDD 5120 x 2880 Display Sierra 10.12 Includes Keyboard and Mouse - Walmart.com
Apple iMac with 5K Retina display (27-inch) review: Apple's 5K iMac impresses expert eyes (review) - CNET